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Epitaxial Graphene : the Ultimate Mirror for Scanning Neutral Helium Microscopy ?

Lundi 14 décembre 2015 11:00 - Duree : 1 heure
Lieu : Science Building - Seminar Room - ESRF - 71 avenue des Martyrs - Grenoble

Orateur : Daniel FARIAS (Depto. Física de la Materia Condensada, Universidad Autónoma de Madrid, Spain)

In recent years, much effort has been devoted to the development of a Scanning Helium Atom Microscope [1-2], in which a focused beam of neutral He atoms is used as imaging probe. I will present a summary of an ongoing EU project devoted to the development of this instrument. The goal of this project is to create a Scanning Helium Atom Microscope with a resolution of about 20 nm, quite similar in setup to a scanning electron microscope, but using a beam of neutral helium atoms to image the surface. This new, Neutral Microscope (NEMI) will be strictly surface sensitive with no penetration into the bulk, due to the low kinetic energy employed ( 50 meV). Such neutral helium beams have been used for surface diffraction studies for many years [3]. The energy is so low that there will be no sample damage even for fragile samples, and no distortion due to charging effect.

After briefly describing the NEMI project, I will summarize recent He-diffraction and phonon dynamics measurements on Ru(0001), Ni(111) and Cu(111) surfaces obtained in our laboratory by means of Helium Atom Scattering. In particular, these results show that a monolayer graphene grown on Ru(0001) can provide an inert surface with high reflectivity (ca. 20%) for thermal He beams. Moreover, this high reflectivity is easily recovered even after extended ( 1 month) exposure to ambient conditions [4]. Both the inertness and such unprecedented high-value of the reflectivity suggest that epitaxial graphene is perhaps the ideal external surface for the NEMI mirror.

Acknowledgments : This work has been supported by the European Union, FP7 : Theme NMP.2012.1.4-3 Grant no. 309672.

References :

[1] R.B. Doak, R.E. Grisenti, S. Rehbein, G. Schmahl, J.P. Toennies and Ch. Woell, Phys. Rev. Lett. 83, 4229 (1999).

[2] M. Koch, S. Rehbein, G. Schmahl, T. Reisinger, G. Bracco, W. E. Ernst and B. Holst, Journal of Microscopy 229, 1 (2008).

[3] D. Farías and K. H. Rieder, Rep. Prog. Phys. 61, 1575 (1998).

[4] M. Minniti et al., App. Phys. Lett. 99, 211907 (2011).

Contact : tellier@ill.fr

Discipline évènement : (Physique)
Entité organisatrice : (ILL)
Nature évènement : (Séminaire)
Evènement répétitif : (General ILL Seminar - College 7)
Site de l'évènement : Polygone scientifique

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